1. Field of the Invention
The present invention relates to features for use with vacuum cleaners having a centrifugal or cyclonic air separation system. More specifically, the present invention relates to a cyclone having a feature such as a helical cyclone expansion region formed on the inner surface of the outer cyclone wall.
2. Description of the Related Art
Referring to FIG. 1, a typical upright vacuum cleaner 100 includes a base 102 that is configured to move along a surface such as a floor, and an upper housing 104 that usually is pivotally mounted to the base 102 and provided with a grip 106 that is used to manipulate and maneuver the device. The downward-facing surface of the base 102 includes a main suction inlet that faces the floor, and through which dirt-laden air is drawn into the device by a motor-driven vacuum fan 108. The vacuum fan 108 may be located in the upper housing 104, as shown, or in the base 102. The main inlet and vacuum fan 108 are in fluid communication by one or more ducts and flexible hoses (not shown) that collectively form a flow path through the vacuum cleaner 100. Ultimately, the air exits the flow path through an outlet to the ambient air. Any number of filtration devices, such as screens, pleated filters, foam filters, and cyclonic separators may be included in the flow path, either upstream or downstream of the vacuum fan 108. Examples of upright vacuum cleaners having these and other features are provided in U.S. Pat. Nos. 7,814,612; 7,163,568; 7,293,326; 7,228,592; 6,829,804 and 7,662,200, which are incorporated herein by reference. For example, the upright vacuum cleaner 100 may have a cyclone chamber 110 located in the upper housing 104. The cyclone chamber 110 or other separation device may alternatively be located in the base 102.
A typical canister vacuum cleaner 200 has a canister body 202 that is connected to a cleaning head 204 by a flexible hose 206 and rigid pipe 208. The pipe 208 often has a grip 210 for manipulating the cleaning head 204. The lower surface of the cleaning head 204 has a suction inlet that is fluidly connected, through the pipe 208 and hose 206, to a vacuum fan (not shown) located inside the canister body 202. As with an upright vacuum cleaner, the canister vacuum cleaner 200 has a flow path in which one or more filtration devices 212 are located. The filtration device 212 usually is in the canister body 202. It is also known to add auxiliary filtration devices, such as a small cyclone separator, to the pipe 208 or cleaning head 204. Examples of canister vacuum cleaners include U.S. Pat. Nos. 3,745,965; 4,953,253; 6,168,641; 6,502,277 and 7,951,214, which are incorporated herein by reference.
Another common variation of a vacuum cleaner is a handheld vacuum cleaner, such as the one shown in U.S. Patent. Publication No. 2007/0271724, which is incorporated herein by reference. Such devices usually comprise a lightweight housing configured for handheld use. Cyclonic separators and other inertial separators are often used in such devices, and it also is common to use a simple filter or bag filter arrangement.
A number of variations of upright and canister vacuum cleaners are known in the art. For example, central vacuum cleaners include a canister that is permanently mounted in a dwelling, and a portable cleaning head that is fluidly connected to the canister by suction tubes distributed throughout the house. Canister vacuums are also often operated as backpack systems with the canister body mounted on the operator's back. Also, upright vacuum cleaners are often scaled down and lightened to form a so-called “stick” vacuum. In some cases, the suction motor and dirt collector may be provided as a handheld or canister unit that can be removed and used separately from an upright, stick, or canister vacuum cleaner.
Cyclonic separation systems of various types have been used in vacuum cleaners. Typically, a cyclonic vacuum uses a rigid cyclone container in place of a bag. The cyclone container typically is cylindrical or somewhat tapered, and includes an inlet that receives dirty air, and an outlet through which cleaned or partially-cleaned air exits. A vacuum fan is used to convey the air through the cyclone container, and the fan may be located upstream or downstream of the cyclone container. As the air passes through the cyclone container, it is directed in a cyclonic pattern to remove dirt and dust from the air flow due to the vortex motion of the cyclone. The removed dirt and dust is deposited in the lower portion of the container or directed into an auxiliary dirt collection container as it drops out of the cyclonic air flow. Auxiliary collection chambers are often mounted to the bottom of the cyclone, but it is also known to place the container to the side. Collection chambers may be located essentially anywhere to receive the dirt being centrifuged out of the airstream.
The air inlet is often provided at an angle relative to the rotational axis of the airflow within the cyclone container to help initiate the cyclonic flow. In some cases, however, the inlet is perpendicular to the axis, in which case a vane or other structure may be located at or near the inlet to initiate cyclonic flow. The air outlet can take any number of forms, such as a simple tube that extends into the cyclone chamber and is open at the end and/or sides.
It is also well known to use more than one cyclone in the air flow path, and multiple series and/or parallel cyclones may be used in a single vacuum cleaner.
Further, filtration features, such as perforated shrouds and other kinds of filter, may be used within the air flow path, either within the cyclone or cyclones, or upstream or downstream of them. For example, a shroud may be used to help direct the air flow within the cylindrical container into a vortex, and to force the airflow to change directions to remove particles by inertia. Shrouds may come in various shapes and sizes, and it is known to provide cylindrical shrouds, conical shrouds, frustroconical shrouds, and shrouds having other shapes. Shrouds may be formed with a mesh type screen, circular perforations, or other apertures or openings to allow air to pass through the shroud while filtering out larger particles. Depending on the application, the perforations may be specifically sized to prevent certain size dust and dirt particles from passing through, while providing relatively little impediment to the airflow.
It is also well known that cyclone shrouds may be provided in the form of microporous filters. Filters used in cyclones may comprise any of various useful types and shapes, such as pleated, foam, ultra-fine, HEPA, ULPA, and so on. Combinations of shrouds and/or microporous filters having various filtration sizes may be used in any number of combinations within or in conjunction with a vacuum cleaner cyclone separator. For example, a perforated shroud or mesh screen may surround a pleated or foam filter to provide plural filtration stages, or a shroud may be formed as two or more stacked filters.
Cyclone shrouds and other kinds of filter also may have other features to enhance airflow or dirt separation. For example, a feature such as a flow reversing lip may be added to a shroud. Flow reversing lips typically are located circumferentially around the bottom lip of the shroud and extend downward, at an angle, or radially, to obstruct the airflow flowing from below the shroud up to the shroud surface. Such flow reversing lips may enhance dirt separation, prevent larger objects from being lifted into contact with the shroud's perforated surface, or provide other benefits. Flow reversing lips are also known as separator plates. Exemplary cyclonic vacuums having shrouds, reversing lips/separator plates, filters, and other filtration and flow controlling devices are described in U.S. Pat. Nos. 5,145,499; 5,893,936; 6,910,245; and 7,222,392, which references are incorporated herein.
It is also known to include airflow modifying features within the cyclone chamber, such as features that disrupt the cyclonic flow pattern to prevent re-entrainment of the dirt (often provided at the bottom of the lower housing where dirt collects). For example, U.S. Pat. No. 7,163,568 shows a stepped cyclone floor that disrupts airflow to separate particles, and U.S. Pat. No. 2,432,757 shows ribs located on the inner and outer walls of a conventional cyclone separator to modify the airflow in the chamber. Other devices include ramp-like ribs that protrude radially into the airflow path; U.S. Pat. No. 3,234,713 shows one such arrangement. It has also been speculated that cyclones having irregular shapes and side chambers of various shapes and sizes, such as those shown in U.S. Pat. No. 6,168,716, can generate multiple cyclones located outside a central cyclone. The foregoing references are incorporated herein by reference.
While various prior art devices like the ones described above have been used in the art, there still exists a need to provide alternatives to such devices.